Leading edge structure for airfoil



Nov. 9, 1954 J M ELLlsoN ET Al.

LEADING EDGE STRUCTURE FOR AIRFOIL Filed Jan. 19, 1952 40//55/1/6 HOA/0LEADING EDGE STRUCTURE FOR AIRFOIL `lohn M. Ellison, Gardena, Raymond I.Moore, Long Beach, and Russell J. Pease, Gardena, Calif., assgnors toNorthrop Aircraft, Inc., Hawthorne, Calif., a corporation of CaliforniaApplication January 19, 1952, Serial No. 267,252

2 Claims. (Cl. 244-123) Our invention relates to sheet stiieners andmore particularly to metal sheets having a backing of styrofoam, anextremely light expanded form of polystyrene plastic, bonded thereto.

In airplane structures, a multiplicity of skin stiifeners are utilizedin what is well known as stressed skin construction. These stiffenersare usually in the form of ribs or light corrugated sheet attached tothe inner side gif 1ihe airplane skin sheets exposed to the airstream inIt is an object of the present invention to provide a sheet stiifener incontact with and securely bonded to substantially the entire free skinarea of the sheet.

In brief the present invention includes a metal sheet having a body ofstyrofoam bonded thereto with an adhesive having high strength bondingcharacteristics to both the metal and the styrofoam. A preferredstructural form of the invention is a sandwich, with styrofoam betweentwo metal sheets and bonded to both. 'Ihe styrofoam stabilizes the sheetto which it is attached, the styrofoam core resisting the greater partof the shear stresses.

The single ligure shows an airplane leading edge member stiiened inaccordance with the present invention. 'Il'his cedge member isessentially a sandwich with one side c ose In the gure, a metal sheet 1of aluminum alloy is formed into a conventional leading edge member 2for an airplane control surface, for example, the member 2 having thecustomary laterally extending stitfeners 3 attached thereto inwardly andrearwardly of the leading edge 4. An interior filler 5 of styrofoam(foamed polystyrene plastic) is cut from a block of the material to litthe interior of member 2. In order that maximum stilening be obtained,the filler 5 is securely bonded to the interior surfaces of sheet 1 andto the front surfaces of lateral stiffeners 3. A satisfactory strongbond to both metal and foam is obtained by the use of the followingadhesive:

100 parts by weight of Epon L-l372 (100% solids) 76 parts by weight ofmethanol ,8% of diethylenetriamine catalyst based on the resin contentof the resultant solution United States Patent O 2,693,922 Patented Nov.9, 1954 dimethyl methane. The adhesive solution when applied has aviscosity of 32 seconds at 70+ as measured by a ZHAN viscosimeter.

The above adhesive is not per se a claimable part of the presentinvention; but forms the subject of the pending U. S. application Ser.No. 240,179, filed August 3, 1951, by Pease.

This adhesive is placed between all metal and styrofoam surfaces to bebonded and allowed to air dry at room temperature for about five hours.No stresses should be applied for about 24 hours thereafter. Theresultant structure has been found to be stronger and lighter than theusual honeycomb core type of stffener heretofore used in similarstructural members. It is also easier to cut, and to vfit into themember.

While in order to comply with the statute, the invention has beendescribed in language more or less specic as to structural features, itis to be understood that the invention is not limited to the specificfeatures shown, but that the means and construction herein disclosedcomprise the preferred form of putting the invention into elfect, andthe invention is therefore claimed in any of its forms or modificationswithin the legitimate and valid scope of the appended claims.

What is claimed is:

1. A stressed skin leading edge structure for aircraft wings and thelike; comprising a unitary metal sheet formed to define a spanwiseextending hollow leading edge structure of airfoil cross section, apreformed core of low density material separately shaped to t andcompletely fill the hollow interior of said leading edge structure andforming the sole support for said skin, a layer of air drying adhesivebetween the interior surface of said metal sheet and the exteriorsurface of said core, the rear edges of said metal sheet being supportedby spanwise extending stiifeners adapted to define faying edges forattaching said leading edge structure to the rcenter section of anaircraft wing or the like.

2. A stressed skin leading edge structure according to claim 1 whereinsaid low density material is foamed polystyrene.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,507,143 Toussaint et al. Sept. 2, 1924 1,874,685 Wright Aug.30, 1932 2,121,052 Roberts et al. June 21, 1938 2,414,125 Rheinfrank,Jr. lan. 14, 1947 2,461,761 Nye Feb. 15, 1949 2,484,141 Alex Oct. 11,1949 2,511,816 Shaw .Tune 13,v 1950 2,512,996 Bixler June 27, 19502,548,447 Shokal et al Apr. 10, 1951 2,566,701 Griese Sept. 4, 19512,574,651 Meyers Nov. 13, 1951 2,576,073 Kropa et al. Nov. 20, 19512,596,818 Meyers May 13, 1952 2,613,893 Young Oct. 14, 1952 2,630,868Ellenberger Mar. 10, 1953

1. A STRESSED SKIN LEADING EDGE STRUCTURE FOR AIRCRAFT WINGS AND THELIKE; COMPRISING A UNITARY METAL SHEET FORMED TO DEFINE A SPANWISEEXTENDING HOLLOW LEADING EDGE STRUCTURE OF AIRFOIL CROSS SECTION, APREFORMED CORE OF LOW DENSITY MATERIAL SEPARATELY SHAPED TO FIT ANDCOMPLETELY FILL THE HOLLOW INTERIOR OF SAID LEADING EDGE STRUCTURE ANDFORMING THE SOLE SUPPORT FOR SAID SKIN, A LAYER OF AIR DRYING ADHESIVEBETWEEN THE INTERIOR SURFACE OF SAID METAL SHEET AND THE EXTERIORSURFACE OF SAID CORE, THE REAR EDGES OF SAID METAL SHEET BEING SUPPORTEDBY SPANWISE EXTENDING STIFFENERS ADAPTED TO DEFINE FAYING EDGES FORATTACHING SAID LEADING EDGE STRUCTURE TO THE CENTER SECTION OF ANAIRCRAFT WING OR THE LIKE.